FIGS. 4, 5A and 5B are a detailed sectional view and general views of a conventional force-on-pedal sensor and pedal-pressure detecting device using the same.
As shown in FIG. 4, spring 23 is positioned between first cover member 21 and second cover member 22 both of which have a U-like glass shape in section, and they are disposed on sensor head 31.
Bellows 32 is formed beneath sensor head 31, and filled with liquid 38. Sensor chip 35 is positioned so as to be immersed in liquid 38, and electrically coupled with terminal 37 via bonding wire 36.
As shown in FIGS. 5A and 5B, pedal section 4 is formed at one end of lever section 5, and force-on-pedal sensor 1 is formed at the other end thereof. Lever section 5 is linked with push-rod 3 using second shaft 10. Arm 7 is formed so as to be contacted with force-on-pedal sensor 1 at load applied point 52, where first shaft 6 operates as a working point and second shaft 10 operates as a supporting point.
An operation of the force-on-pedal sensor is discussed hereinafter with reference to FIG. 4. When force-on-pedal is applied on first cover member 21, the force-on-pedal is transmitted through spring 23 to second cover member 22 and pushes sensor head 31. This pushing force is transmitted to sensor chip 35 by liquid 38, whereby the force-on-pedal is detected. Thus, the force-on-pedal is outputted as an electric signal through bonding wire 36 and terminal 37.
An operation of the pedal-pressure detecting device is discussed hereinafter with reference to FIGS. 5A and 5B. When the force-on-pedal is not more than 200N, second shaft 10 does not contact a circumference of hole 9, and a load is applied to force-on-pedal sensor 1 from load applied point 52 via arm 7. The load applied at load applied point 52 is attenuated rather than a load applied to first shaft 6 because of leverage formed by arm 7, second shaft 10 and first shaft 6. An attenuation ratio is determined by a ratio of a distance between load applied point 52 and second shaft 10 to a distance between second shaft 10 and first shaft 6.
As shown in FIG. 5B, when the force-on-pedal exceeds more than 200N, second shaft 10 contacts the circumference of hole 9, so that no more load is applied to force-on-pedal sensor 1.
An example of the force-on-pedal sensor mentioned above is disclosed in Unexamined Japanese Patent Publication No. 2002-205628. However, the conventional force-on-pedal sensor has a complicated structure because it is required an airtight characteristic to seal liquid 38, so that structural reliability is low.
In addition, if bellows 32 is injured in assembling, liquid 38 is leaked and a detecting function of the sensor is impaired, therefore handling is not easy.
The present invention is directed to solve the problems pointed out above and provides a force-on-pedal sensor having a simple structure, high structural reliability and easy-handling.